The present application claims priority to Japanese Application No. P2000-041439 filed Feb. 15, 2000, which application is incorporated herein by reference to the extent permitted by law.
The present invention relates to a nonaqueous electrolyte battery including a container sealed with a sealing lid, and a method of producing the nonaqueous electrolyte battery.
In recent years, along with progress of the electronic technology, there has been a tendency toward high performance, miniaturization, and portableness of electronic equipment. Batteries used for the electronic equipment have been correspondingly required to have high energy densities, and to meet such a requirement, studies have been actively made to develop nonaqueous electrolyte batteries. In particular, lithium batteries or lithium ion secondary batteries, having performances higher than those of conventional batteries, for example, a high electromotive force of 3 or 4 V, have been adopted for various types of portable electronic equipment, such as a camcorder, a portable telephone, and a notebook type personal computer.
As an electrolytic solution for a lithium or lithium ion battery, there has been used a solution obtained by dissolving an electrolyte exemplified by a lithium based electrolyte salt such as LiPF6 in a nonaqueous solvent exemplified by a carbonate such as low molecular ethylene carbonate, propylene carbonate, or diethyl carbonate. This is because such an electrolytic solution has a relatively high conductivity and exhibits a stable potential.
In the above-described nonaqueous electrolyte battery, an electrolytic solution contains an organic solvent as described above, and accordingly, when wiring of the battery is short-circuited or the battery is abnormally heated for example, the electrolytic solution may be vaporized and decomposed to generate gas. If the generation rate of such a gas becomes a specific value or more, an inner pressure of an enclosed container may be rapidly raised.
To cope with such an abnormality, there is known a nonaqueous electrolyte battery 100 having a mechanism shown in FIG. 1.
The nonaqueous electrolyte battery 100 includes an electrode body 104 formed by spirally winding a stack of a positive electrode 101, a separator 102, and a negative electrode 103; a container 105 for containing the electrode body 104; an insulating plate 106 disposed on a bottom portion of the container 105, for preventing the electrode body 104 from being brought into electric contact with the container 105; and a sealing lid group 107 fixed by caulking to an opening at the upper end of the container 105 via an insulating gasket 113. The sealing lid group 107 includes a disk-like inner lid body 108 disposed opposite to the electrode body 104; a PTC element 110 disposed on an ring portion of the inner lid body 108 via a valve film 109 formed of a flexible thin film; and a cap-shaped battery lid 111 disposed with its peripheral edge being in contact with the PTC element 110. Each of the inner lid body 108 and the PTC element 110 has at its central portion a though-hole, and the battery lid 111 has at its stepped portion vent holes 111a. One end of a positive electrode lead 112 is connected to the positive electrode 101 of the electrode body 104, and the other end thereof is connected to a back surface of the inner lid body 108 of the sealing lid group 7.
In the nonaqueous electrolyte battery 100 having the above-described configuration, if a current larger than a normal current is applied to the battery 100, for example, by over-charging, the resistance of the PTC element 110 positioned between the inner lid 108 and the battery lid 111 is rapidly increased with temperature rise, to stop the supply of current, thereby preventing an increase in inner pressure in the nonaqueous electrolyte battery 100. Further, if a decomposition gas is generated and thereby the inner pressure in the nonaqueous electrolyte battery 100 reaches a specific pressure, the decomposition gas passes through the though-hole opened in the inner lid body 108, to break or melt the valve film 109 positioned over the inner lid body 108. As a result, the decomposition gas is discharged to the outside of the nonaqueous electrolyte battery 100 through the broken portion of the valve film 109, the through-hole opened in the PTC element 110, and the vent holes 111a opened in the battery lid 111, to thereby reduce the inner pressure in the nonaqueous electrolyte battery 100.
By the way, as shown by arrows I in FIG. 1, part of the decomposition gas discharged from the broken portion of the valve film 109 is directly discharged to the outside of the nonaqueous electrolyte battery 100 through the vent holes 111a of the battery lid 111 without collision with the inner side of the battery lid 111. The part of the decomposition gas, which directly passes through the vent holes 111a, is discharged obliquely with respect to the height direction of the nonaqueous electrolyte battery 100, to thereby give a motive force to the nonaqueous electrolyte battery 100.
FIG. 2 is an enlarged view showing a circle portion H in FIG. 1. Referring to FIG. 2, part of the decomposition gas once collides with the inner side of a projecting portion of the battery lid 111 as shown by an arrow J, and is discharged from the vent holes 111a along the direction substantially perpendicular to the height direction of the nonaqueous electrolyte battery 100 as shown by arrows K. Part of the decomposition gas discharged in such a direction, however, collides with a caulking portion formed by inwardly bending an opening edge of the container 105, and flows in the height direction of the nonaqueous electrolyte battery 100 as shown by arrows L.
As a result, there arises a problem that the nonaqueous electrolyte battery 100 is moved by a motive force generated by the discharge of the decomposition gas, to exert adverse effect on peripheral equipment. Further, the decomposition gas having broken the valve film 109 is discharged from the vent holes 111a at a high speed, whereby the motive force given to the nonaqueous electrolyte battery 100 becomes larger. As a result, there arises a problem that the movement of the nonaqueous electrolyte battery 100 by the discharge of the decomposition gas becomes larger.
An object of the present invention is to provide a nonaqueous electrolyte battery capable of preventing the movement of the nonaqueous electrolyte battery by a motive force generated by discharge of a decomposition gas generated in an abnormal state, and a method of producing the nonaqueous electrolyte battery.
To achieve the above object, according to a first aspect of the present invention, there is provided a nonaqueous electrolyte battery including: an electrode body having at least a positive electrode and a negative electrode; a cylindrical container with its bottom closed, in which the electrode body and a nonaqueous electrolytic solution are contained; and a lid body for closing an opening portion of the container; wherein the lid body has a lid portion which constitutes a peripheral edge portion of the lid body, a projecting portion which constitutes a central portion of the lid body, and a stepped portion which has a vent hole and is positioned between the lid portion and the projecting portion; and a metal plate having a through-hole is disposed between the lid body and the electrode body.
With this configuration, a decomposition gas generated in the container in an abnormal state passes through the through-hole of the metal plate, and at this time, the discharge path of the decomposition gas is suitably restricted in the radial direction of the container, whereby the decomposition gas collides with the inner side of the lid body. As a result, it is possible to sufficiently damp the discharge speed of the decomposition gas and to control the discharge direction of the decomposition gas along the direction substantially perpendicular to the height direction of the battery.
According to a second aspect of the present invention, there is provided a nonaqueous electrolyte battery including: an electrode body having at least a positive electrode and a negative electrode; a cylindrical container with its bottom closed, in which the electrode body and a nonaqueous electrolytic solution are contained; and a lid body for closing an opening portion of the container; wherein the lid body has a lid portion which constitutes a peripheral edge portion of the lid body, a projecting portion which constitutes a central portion of the lid body, and a stepped portion which has a vent hole and is positioned between the lid portion and the projecting portion; and the projecting portion is formed into an approximately circular shape, and is substantially flattened; and letting a diameter of the substantially flattened portion be A and an outside diameter of the container be C, C and A satisfy a relationship of 0.55xe2x89xa6A/Cxe2x89xa61.
With this configuration, a decomposition gas generated in the container in an abnormal state once collides with the inner side of the lid body, with a result that the discharge speed of the decomposition gas is damped, and the discharge direction of the decomposition gas is controlled in the direction substantially perpendicular to the height direction of the battery, whereby the decomposition gas is discharged to the outside of the battery through the vent hole of the lid body.
According to a third aspect of the present invention, there is provided a nonaqueous electrolyte battery including: an electrode body having at least a positive electrode and a negative electrode; a cylindrical container with its bottom closed, in which the electrode body and a nonaqueous electrolytic solution are contained; and a lid body for closing an opening portion of the container; wherein the lid body has a lid portion which constitutes a peripheral edge portion of the lid body, a projecting portion which constitutes a central portion of the lid body, and a stepped portion which has a vent hole and is positioned between the lid portion and the projecting portion; the lid body is held by a caulking portion formed by inwardly bending an outer peripheral edge of an opening portion of the container; a height of an end portion, on the projecting portion side, of the vent hole is intermediate between the top of the caulking portion and the projecting portion; and letting a difference in height between the top of the caulking portion and the end portion, on the projecting portion side, of the vent hole be D, and the total height of the battery including the container and the lid body be E, D and E satisfy a relationship of 0.01xe2x89xa6D/Exe2x89xa60.1.
With this configuration, the flow direction of the decomposition gas discharged from the vent hole of the lid body is not blocked by the caulking portion. As a result, the decomposition gas flows along the direction substantially perpendicular to the height direction of the battery.
According to a fourth aspect of the present invention, there is provided a method of producing a nonaqueous electrolyte battery, including the steps of: putting an electrode body having at least a positive electrode and a negative electrode in a cylindrical container with its bottom closed; pouring a nonaqueous electrolytic solution in the container; disposing a metal plate having a through-hole over the electrode body; and placing a lid body on the metal plate in such a manner that an opening portion of the container is closed with the lid body, the lid body having a lid portion which constitutes a peripheral edge portion of the lid body, a projecting portion which constitutes a central portion of the lid body, and a stepped portion which has a vent hole and is positioned between the lid portion and the projecting portion.
With this configuration, it is possible to easily produce a nonaqueous electrolyte battery capable of controlling the discharge direction of a decomposition gas.